[PATCH] D127531: [SLP]Improve analysis of same/alternate code ops and scheduling.

[Valeriy Dmitriev via Phabricator via llvm-commits]

vdmitrie added inline comments.


================
Comment at: llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp:1251
+                  getUnderlyingObject(LI2->getPointerOperand()))
+            return LookAheadHeuristics::ScoreAltOpcodes;
           return LookAheadHeuristics::ScoreFail;
----------------
ABataev wrote:
> vdmitrie wrote:
> > I'm not sure I understand why this is scored as alternating opcodes.
> > If underlying objects are same that probably means Dist variable must have a value and the value is 0.
> > i.e. these loads are from same location. right?  It sounds like splat load. 
> > Where alternating opcodes come from?
> No. If you have Geps with non-const indices, the Dist might be None. But the loads still may be the source of masked gather.
> No. If you have Geps with non-const indices, the Dist might be None. But the loads still may be the source of masked gather.

Ah. right. I forgot that we now vectorize non-const indices. But still, why alternate opcode?
It sounds like we need to introduce named constant dedicated to gather.


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https://reviews.llvm.org/D127531